1. Field of the Invention
The present invention relates to a roof structure and, more particularly, to a vehicle roof structure including a movable roof panel for opening and closing an opening in the roof of a vehicle.
2. Description of the Prior Art
A popular option in the automotive market is a roof vent more commonly referred to as a sunroof or, as it is called when a panel which forms part of the vent is made of a transparent material such as glass, a moonroof. A particularly popular type of roof vent is a sliding and venting sunroof. Such a sunroof has a movable roof panel which is slidable between closed and open positions in an opening formed in the roof of a vehicle as well as being pivotable about its front end to raise the rear edge of the roof panel a small amount above a stationary roof structure, i.e., into a "venting" position. Typically, the roof panel is formed of metal or glass. It is also common for sunroofs to be provided with electrically powered drive mechanisms which operate to move the movable roof panel. Examples of heretofore developed sliding and venting sunroofs may be seen in U.S. Pat. No. 4,420,184 to KALTZ and U.S. Pat. Nos. 4,650,243 and 4,652,045 to HANLEY et al.
There are a multitude of desired characteristics of sunroofs. Of course, it is desirable that sunroofs be reliable, easy to service and smooth and quiet in operation. Along this line, the fewer movable parts that make up the sunroof mechanism, generally the better. Also, with respect to smooth operation, it is important that drive mechanisms do not become unbalanced so as to cause the moving roof panel to be no longer positioned or stressed evenly on both sides. Certain prior art drive systems, especially those employing a drive cable, are prone to becoming unbalanced. Details regarding prior art cable drive systems are set forth in U.S. Pat. No. 4,749,227 to BIENERT et al. and in U.S. Pat. No. 4,752,099 to ROOS et al. In addition, it is important that sunroofs be safe. Along this line, sunroofs must remain fixed in their various positions notwithstanding the strong pressures applied on them from different directions. For example, sunroofs must remain closed even when car doors are slammed, compressing the air inside the vehicle and exerting a strong upward force on the sunroof. Also, it is important that sunroofs do not close when it is not intended that they close, otherwise a person (or object) in the way of the closing roof panel could become injured (or damaged). Yet another factor contributing to safety is the inclusion of shielding between the car interior and moving parts of the sunroof mechanism. Such shielding can also be designed to enhance the appearance of the sunroof, making it more attractive to potential purchasers and users. Further, it is desirable that sunroofs be quick and easy to install. This reduces the labor costs of becoming a sunroof owner, making the option more attractive to potential purchasers. Still further, because of the recent trend towards smaller and lighter weight vehicles, it is becoming increasingly important that sunroofs be compact and lightweight. Large sunroof mechanisms can dramatically reduce headroom in a vehicle; this can be a severe problem in a vehicle that already has very little headroom.
From the foregoing, it should be apparent that it is extremely difficult to design a sunroof that possesses all of the desired characteristics of sunroofs. In fact, an aspect of a sunroof that enhances the sunroof in one respect will very likely detract from the sunroof in another respect. For example, adding shielding for safety and appearance purposes increases size and weight which are undesirable in today's smaller cars. Likewise, adding locking mechanisms also increase weight and may increase mechanism size. Each part added to a sunroof for any reason makes the sunroof somewhat less reliable and more difficult to service. These types of trade-offs could be further set forth at length.
Accordingly, it should also be apparent that there is a continuing need for an improved sunroof, that is, a sunroof that has a maximum number of the desired characteristics set forth above, while having a minimum number of shortcomings, if any.